Computer input methods and systems that track movements of users with a digital camera are limited to analyzing visible features, such as the hands, head or eyes. However, such anatomical features vary significantly from one person to the next, and the apparent shapes of such visible anatomical features vary widely depending upon the orientation of the imaged anatomy, user expression, etc. Consequently, such visual tracking systems may exhibit significant positioning errors, both in recognizing the features to be tracked and in accurately determining their location and orientation in three-dimensional space.